This invention relates to miniaturized devices for delivery of chemical molecules, and more particularly to controlled time and rate release multi-welled delivery devices.
Drug delivery is an important aspect of medical treatment. The efficacy of many drugs is directly related to the way in which they are administered. Some therapies require that the drug be repeatedly administered to the patient over a long period of time. This makes the selection of a proper drug delivery method problematic. Patients often forget, are unwilling, or are unable to take their medication. Drug delivery also becomes problematic when the drugs are too potent for systemic delivery. Therefore, attempts have been made to design and fabricate a delivery device, which is capable of the controlled, pulsatile, or continuous release of a wide variety of molecules including, but not limited to, drugs and other therapeutics.
U.S. Pat. No. 5,797,898 to Santini Jr., et al. discloses microchip delivery devices which have a plurality, typically hundreds to thousands, of tiny reservoirs in which each reservoir has a reservoir cap positioned on the reservoir over the molecules, so that the molecules, e.g., drugs, are released from the device by diffusion through or upon disintegration of the reservoir caps. The reservoirs may have caps made of a material that degrades at a known rate or that has a known permeability (passive release), or the caps may include a conductive material capable of dissolving or becoming permeable upon application of an electrical potential (active release). It would be useful, however, to utilize other methods for triggering release, particularly when the presence of an electrolyte is not convenient or possible. It also would be advantageous to provide active release without the limitation that the cap material include a conductive material capable of disintegrating or becoming permeable upon application of an electrical potential.
It is therefore an object of the present invention to provide a multi-welled delivery device for drugs and other molecules that does not require the presence of an electrolyte.
It is another object of the present invention to provide a multi-welled delivery device for active release of drugs and other molecules that does not require conductive reservoir cap or direct application of an electrical potential.
Microchip delivery devices are provided that control both the rate and time of release of molecules, wherein the device includes a substrate, at least one reservoir in the substrate containing the molecules (i.e. a release system), and a reservoir cap positioned on the reservoir over the molecules, wherein the molecules are released from the reservoir upon heating or cooling the device or a portion thereof sufficient to rupture the reservoir cap. In a preferred embodiment, the device includes a resistor integrated into the reservoir or mounted near or on the reservoir cap, which upon application of an electric current through the resistor, causes at least one of the contents of the reservoir to thermally expand, vaporize, phase change, or undergo a thermally driven reaction, such that the reservoir cap ruptures due to mechanical stress. Alternatively, the thermal trigger can be a temperature change to the entire device (e.g., without application of resistive heating) due for example to the placement onto or into the body, or otherwise caused by a significant change in the temperature of the environment in which the device is placed. In another embodiment, the device includes reservoir caps that rupture due to expansion, contraction, or phase change of the cap material in response to a temperature change. In yet another embodiment, the device includes reservoir caps or release systems that become more permeable to the molecules in response to a temperature change.
The reservoir cap preferably is a thin film of a material having a yield or tensile strength beyond which the material fails by fracture or some other form of mechanical failure. Alternatively, the reservoir cap could be made of material that loses structural integrity when it undergoes a phase change in response to a change in temperature. Examples of such materials include metals, glasses, ceramics, and polymers, such as semicrystalline polyesters.
The devices can be designed to provide release in either a continuous or pulsatile manner. The microchips provide control over the rate the molecules are released as well as the time at which release begins. In one embodiment, the thermal trigger for a reservoir can be controlled by a preprogrammed microprocessor, remote control, or by a signal from a biosensor.
The reservoirs can contain multiple drugs or other molecules in variable dosages. Each of the reservoirs of a single microchip can contain different molecules and/or different amounts and concentrations, which can be released independently. Examples of molecules to be delivered include drugs, fragrances, dyes or coloring agents, sweeteners, diagnostic reagents, and compounds used in tissue culture, such as cellular growth factors.